FIELD OF THE INVENTION
The present invention relates to a solid polymer electrolyte to be used in batteries, electrochromic displays, condensers and other electrochemical devices.
Hitherto, solid polymer electrolytes have included complexes composed of a polymer material having polyethylene oxide, polypropylene oxide or ethylene oxide-propylene oxide copolymer in the main chain or side chains and an alkali metal salt or alkaline earth metal salt.
The polyether material in the solid polymer electrolyte has the drawback that it inconveniently softens at an elevated temperature and the mechanical strength thereof is thereby lowered since it has a low glass transition temperature (for instance, the glass transition temperature of polyethylene oxide is -67.degree. C.).